The present invention relates to an optical switch which is compact, inexpensive, and easily fabricated.
A great deal of development is being undertaken for optical telecommunication using optical fibers as a transmission medium, and it is being put into practice aggressively in the fields of public communication trunk lines, power plants, industrial plants, building management systems, office automation (OA), factory automation (FA), and local area networks (LAN). In application of optical communication to these industrial fields, system component parts will soon be required to be of low cost, and therefore it is material to establish the technologies for the miniaturization, simplification of assembly and volume production of component parts and equipment.
Conventionally, system equipment and component parts, such as transmission modules and optical switches, have been manufactured separately for each functional demand. An example of the conventional optical LAN system (loop type) is shown conceptually in FIG. 2, in which a central controller (CPU) 1 distributes data (Optical signals) over an optical transmission fiber cable 2 to a plurality of terminals (ST1-ST5) 4. At each branch point, an optical station 3 is provided individually, which needs to be equipped with an optical switch for transmitting optical signals to the terminal 4 selectively. The conventional optical switch, as shown by reference number 5 in FIG. 3, is equipped separately from and in front of an optical transmission module 7 including a photosensitive element 8 and light emitting element 9. In FIG. 3, further reference number 6 denotes a light path selector in the optical switch 5, number 10 denotes an interfacing logical converter, number 11 denotes an optical input signal, 12 denotes an optical output signal, 13 denotes optical couplers connecting the optical switch 5 and optical transmission module 7, and number 14 denotes a switching signal line for operating the optical switch 5. The junctions between the transmission fiber cable 2 and optical switch 5 and between the optical switch 5 and optical transmission module 7 necessitate the optical connection, which increases in number as the number of terminal units 4 in the optical LAN system increases. However, optical connections which often require a difficult work for resistering optical axes and the like are preferably as small in number as possible in constructing an optical LAN system. A larger number of connections, as in the case of FIG. 3, imposes restrictions on the transmission distance and the number of terminal units installed in the system, and also problems of increased cost of the switch periphery component parts and increased optical coupling loss.
A prior art optical switch of this kind has employed a mechanism (prism) as disclosed, for example, in Japanese Patent Laid-open Publication No. 57-139704, however, the prism mechanism for light path switching has required a significant space and hampered the compactness.
A prior art optical transmission module disclosed in Japanese Patent Laid-open Publication No. 55-117114 has been arranged separately for the optical circuit including lenses, etc. and the electrical circuit, and therefore it has been difficult to mount the optical switch directly on the module section or to accommodate the module within the optical switch.